1. Field of the Invention
The present invention relates to a moving image processing method and apparatus and, more particularly, to a moving image processing method and apparatus capable of efficient transfer of moving image data without data access conflict.
2. Description of the Prior Art
In conventional moving image processing apparatuses, various methods for storing moving image data have been proposed:
(1) A storing method in which only the moving image data is stored without additional information such as scene-change; PA1 (2) A method in which moving image administrative information, such as the resolution or the total frame number of moving image data, is added as a header or added to the end of the data; PA1 (3) A method in which moving image data and the moving image administrative information of the data are separately stored in the form of files in a common storage medium such as a hard disk; PA1 (4) A method for storing the moving image data by frame when the compression of a moving image data is not performed. Each of the frames is stored as one file; and PA1 (5) A method based on Moving Image Coding Scheme being standardized by the MPEG (Moving Picture Coding Experts Group), a working group of the ISO (International Organization for Standardization). In this method, VLC (variable length code) Huffman coding is employed for the compression of a moving image data. The basic algorithm of this method is motion compensation+DCT (Discrete Cosine Transform).
This method is for storing moving image data having different lengths of frames.
In the above methods, when stored moving image data has no additional information, it is impossible to provide any operation other than forward or reverse playback. In a case where a common storage medium such as a hard disk stores moving image administrative information as well as moving image data, if a moving image data is designated to be displayed while other moving image data is being displayed, or if moving image administrative information is designated to be read out in mid-course of displaying moving image data, there is the possibility of an access conflict, as a result of which the display speed of the currently displayed image data cannot be kept at 30 frames/second. In a case where a user manages moving image data as one file and moving image administrative information as another in a common storage medium, a conceivable drawback is that the correspondence between a moving image and its administrative information can not be established. In this case, the moving image data and the moving image administrative information being inconsistent may be deleted inadvertently, disturbing the relation of other moving image data and corresponding administrative information.
When data compression is performed on the basis of the method proposed by the MPEG, if moving image data has no moving image administrative information, there is no access to an object frame of the data from which the data is to be replayed without searching from the start to the end of the data. The problem is that the above retrieval is inefficient.
In comparison with a still image processing apparatus, a moving image processing apparatus processes much more data. For this reason, a conventional moving image processing apparatus requires a hard disk with a large capacity for accumulating a huge amount of moving image data and a high-speed disk interface for displaying image data at a speed of about 30 frames/sec. If the input-output speed of the hard disk is not up to a predetermined standard, the apparatus further requires an image memory for temporary storage or a semi-conductor disk equipped as an input-output unit.
However, in the aforementioned apparatus, the input-output speed of the disk interface is too slow to keep the 30 frames/sec speed for reading out image data.
Accordingly, in order to maintain the above speed, the size of the image is reduced or data compression is performed, causing the problem that moving image data of high quality cannot be reproduced. Another drawback is that an apparatus equipped with a large-capacity hard disk and a high-speed disk interface costs a great deal, while an apparatus having a small-capacity hard disk can not store a large amount of moving image data, nor a moving image of high quality.
The structure of the apparatus including an image memory for temporary storage or a semi-conductor disk realizes desired high-speed read-out, but the data storage capacity is limited due to the memory capacity or the capacity of the semi-conductor disk, and besides, all these devices are expensive.
The conventional apparatus can store a plurality of original moving image data by adopting storage media such as removable OMD's (optical-magnetic disk). Such additional storage media might be employed in storing the enormous amount of data. In this case, however, no advancement in the point of image quality can be expected, considering that the input-output speed and the access speed of the disk interface thereof is slow.